Overexcavation depth on expansive shales.
Overexcavation depth on expansive shales.
(OP)
Is there a typical depth of overexcavation and fill replacement under foundations on expansive shales?
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Overexcavation depth on expansive shales.
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RE: Overexcavation depth on expansive shales.
It will depend upon how expansive the soil/shale is, how you are loading it and what the structure is.
First step should be several lab tests to determine how expansive the soil is.
RE: Overexcavation depth on expansive shales.
RE: Overexcavation depth on expansive shales.
RE: Overexcavation depth on expansive shales.
RE: Overexcavation depth on expansive shales.
RE: Overexcavation depth on expansive shales.
The conditions needs to be "right" for this bio-chemical reaction to occur. It can be mitigated by keeping the shale away from air, permanent submergence works if you can deal with the other issues associated with it. Sealing with bitumens has been tried but seems to be less than permanent. The reaction is worse under warm areas, like boiler rooms.
Drilled piles and a structural basement slab, with an expansion buffer is another successful strategy.
Another is to build a raft stiff enough to carry the swell load back to the columns, sort of an upside down uniform load on a two way column supported slab.
RE: Overexcavation depth on expansive shales.